"The effects of PAM on the individuals who contract the amoeba are tragic," Dr. Carina Blackmore, a Florida Department of Health interim state epidemiologist, told CBS News.

Reyna was hospitalized over the weekend because of flu-like symptoms. Friends and family members believe he contracted the amoeba while playing in a canal, though Glade County Health Department officials aren't sure yet where he was exposed to the disease.

"There's really no way to pinpoint the water or soil source because it's naturally occurring," spokeswoman Brenda Barnes told the News-Press.

To raise awareness about their son's condition, Reyna's parents created on a Facebook page, which they updated on Tuesday. "Doctors are saying things have not changed. We are still strong on our end because we know God will step in when He is ready. Keep praying. I feel this is much bigger than my Zac," the update reads.

Naegleria fowleri infections often occur from swimming in warm freshwater lakes or streams with low-water levels. According to the CDC, the single-cell organism can travel up your nose, where it multiplies and eventually begins to eat your brain. It has a 99 percent fatality rate, though it is still relatively rare; between 2003 and 2012, only 31 infections were reported in the US. But that might be changing soon, thanks to global warming.